Compound nitride semiconductors, such as III-V semiconductors, are gaining popularity as promising alternatives or complements beyond silicon due to their large band gap electrical properties. Using large band gap materials in semiconductor technology yields semiconductor devices with high breakdown voltages and high electron mobility. Conventional devices utilizing wide band gap semiconductors are formed with a planar semiconductor structure including a single gate electrode and a pair of source and drain regions. In order to fabricate conventional planar wide band gap transistors, thick buffer layers of III-V semiconductor material are initially formed on a bulk substrate to minimize threading dislocation defects. Practically speaking, growing thick buffer layers can be costly and time consuming, thereby limiting flexibility in the design process.